This invention relates to an improved process for the production of para alkyl phenol. It particularly relates to an improved continuous process for the production of para alkyl phenol in which the alkyl group is derived from a low molecular weight polypropylene.
In conventional processes for preparing alkyl phenols, phenol is alkylated with a source of an alkyl group, usually an olefinic hydrocarbon, for example a polyolefin, in the presence of an alkylation catalyst. It is known that, in general, strong acid catalyzed phenol alkylation is selective and that para alkyl phenol is initially formed. Rearrangement to the ortho isomer, however, is a facile concurrent or subsequent reaction, especially where the alkylation agent is a labile group, such as a tertiary olefin, and the catalyst is a strong acid. For use as a lube oil additive, para monoalkyl phenols are, in general, superior to the corresponding ortho isomers, the latter exhibiting undesirable effects upon lube oil viscosities and the like. In order to avoid undesirable production of ortho alkyl phenol, it has been conventional to employ weak acid catalysts, acidic resins, and water moderated inorganic acids, as well as acidic clays and the like. The penalty in such is that long contact or reaction times (six to eight hours) are usually required. These long reaction periods are not satisfactory for continuous processing.
An object of this invention is to provide a continuous process for selectively producing para mono alkyl phenols in high yield and at a rapid rate. Other objects will be evident from the examples and description to follow.